lfs: add a local store method for opening a blob

The has() and read() methods already dynamically switch between the usercache
and local store.  This should generally be preferred to directly accessing the
vfs instances outside of the store.

The file is now explicitly opened in binary mode for clarity.  (It was also
being opened in binary mode before, but only because vfs.__call__() appends 'b'
if needed when not opening with 'text=True'.)

hgext/lfs/blobstore.py

@@ -1,434 +1,442
 # blobstore.py - local and remote (speaking Git-LFS protocol) blob storages
 #
 # Copyright 2017 Facebook, Inc.
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 import hashlib
 import json
 import os
 import re
 import socket
 
 from mercurial.i18n import _
 
 from mercurial import (
     error,
     pathutil,
     url as urlmod,
     util,
     vfs as vfsmod,
     worker,
 )
 
 from ..largefiles import lfutil
 
 # 64 bytes for SHA256
 _lfsre = re.compile(r'\A[a-f0-9]{64}\Z')
 
 class lfsvfs(vfsmod.vfs):
     def join(self, path):
         """split the path at first two characters, like: XX/XXXXX..."""
         if not _lfsre.match(path):
             raise error.ProgrammingError('unexpected lfs path: %s' % path)
         return super(lfsvfs, self).join(path[0:2], path[2:])
 
     def walk(self, path=None, onerror=None):
         """Yield (dirpath, [], oids) tuple for blobs under path
 
         Oids only exist in the root of this vfs, so dirpath is always ''.
         """
         root = os.path.normpath(self.base)
         # when dirpath == root, dirpath[prefixlen:] becomes empty
         # because len(dirpath) < prefixlen.
         prefixlen = len(pathutil.normasprefix(root))
         oids = []
 
         for dirpath, dirs, files in os.walk(self.reljoin(self.base, path or ''),
                                             onerror=onerror):
             dirpath = dirpath[prefixlen:]
 
             # Silently skip unexpected files and directories
             if len(dirpath) == 2:
                 oids.extend([dirpath + f for f in files
                              if _lfsre.match(dirpath + f)])
 
         yield ('', [], oids)
 
 class filewithprogress(object):
     """a file-like object that supports __len__ and read.
 
     Useful to provide progress information for how many bytes are read.
     """
 
     def __init__(self, fp, callback):
         self._fp = fp
         self._callback = callback # func(readsize)
         fp.seek(0, os.SEEK_END)
         self._len = fp.tell()
         fp.seek(0)
 
     def __len__(self):
         return self._len
 
     def read(self, size):
         if self._fp is None:
             return b''
         data = self._fp.read(size)
         if data:
             if self._callback:
                 self._callback(len(data))
         else:
             self._fp.close()
             self._fp = None
         return data
 
 class local(object):
     """Local blobstore for large file contents.
 
     This blobstore is used both as a cache and as a staging area for large blobs
     to be uploaded to the remote blobstore.
     """
 
     def __init__(self, repo):
         fullpath = repo.svfs.join('lfs/objects')
         self.vfs = lfsvfs(fullpath)
         usercache = lfutil._usercachedir(repo.ui, 'lfs')
         self.cachevfs = lfsvfs(usercache)
         self.ui = repo.ui
 
+    def open(self, oid):
+        """Open a read-only file descriptor to the named blob, in either the
+        usercache or the local store."""
+        if self.cachevfs.exists(oid):
+            return self.cachevfs(oid, 'rb')
+
+        return self.vfs(oid, 'rb')
+
     def write(self, oid, data, verify=True):
         """Write blob to local blobstore."""
         if verify:
             _verify(oid, data)
 
         with self.vfs(oid, 'wb', atomictemp=True) as fp:
             fp.write(data)
 
         # XXX: should we verify the content of the cache, and hardlink back to
         # the local store on success, but truncate, write and link on failure?
         if not self.cachevfs.exists(oid):
             if verify or hashlib.sha256(data).hexdigest() == oid:
                 self.ui.note(_('lfs: adding %s to the usercache\n') % oid)
                 lfutil.link(self.vfs.join(oid), self.cachevfs.join(oid))
 
     def read(self, oid, verify=True):
         """Read blob from local blobstore."""
         if not self.vfs.exists(oid):
             blob = self._read(self.cachevfs, oid, verify)
 
             # Even if revlog will verify the content, it needs to be verified
             # now before making the hardlink to avoid propagating corrupt blobs.
             # Don't abort if corruption is detected, because `hg verify` will
             # give more useful info about the corruption- simply don't add the
             # hardlink.
             if verify or hashlib.sha256(blob).hexdigest() == oid:
                 self.ui.note(_('lfs: found %s in the usercache\n') % oid)
                 lfutil.link(self.cachevfs.join(oid), self.vfs.join(oid))
         else:
             self.ui.note(_('lfs: found %s in the local lfs store\n') % oid)
             blob = self._read(self.vfs, oid, verify)
         return blob
 
     def _read(self, vfs, oid, verify):
         """Read blob (after verifying) from the given store"""
         blob = vfs.read(oid)
         if verify:
             _verify(oid, blob)
         return blob
 
     def has(self, oid):
         """Returns True if the local blobstore contains the requested blob,
         False otherwise."""
         return self.cachevfs.exists(oid) or self.vfs.exists(oid)
 
 class _gitlfsremote(object):
 
     def __init__(self, repo, url):
         ui = repo.ui
         self.ui = ui
         baseurl, authinfo = url.authinfo()
         self.baseurl = baseurl.rstrip('/')
         useragent = repo.ui.config('experimental', 'lfs.user-agent')
         if not useragent:
             useragent = 'mercurial/%s git/2.15.1' % util.version()
         self.urlopener = urlmod.opener(ui, authinfo, useragent)
         self.retry = ui.configint('lfs', 'retry')
 
     def writebatch(self, pointers, fromstore):
         """Batch upload from local to remote blobstore."""
         self._batch(pointers, fromstore, 'upload')
 
     def readbatch(self, pointers, tostore):
         """Batch download from remote to local blostore."""
         self._batch(pointers, tostore, 'download')
 
     def _batchrequest(self, pointers, action):
         """Get metadata about objects pointed by pointers for given action
 
         Return decoded JSON object like {'objects': [{'oid': '', 'size': 1}]}
         See https://github.com/git-lfs/git-lfs/blob/master/docs/api/batch.md
         """
         objects = [{'oid': p.oid(), 'size': p.size()} for p in pointers]
         requestdata = json.dumps({
             'objects': objects,
             'operation': action,
         })
         batchreq = util.urlreq.request('%s/objects/batch' % self.baseurl,
                                        data=requestdata)
         batchreq.add_header('Accept', 'application/vnd.git-lfs+json')
         batchreq.add_header('Content-Type', 'application/vnd.git-lfs+json')
         try:
             rawjson = self.urlopener.open(batchreq).read()
         except util.urlerr.httperror as ex:
             raise LfsRemoteError(_('LFS HTTP error: %s (action=%s)')
                                  % (ex, action))
         try:
             response = json.loads(rawjson)
         except ValueError:
             raise LfsRemoteError(_('LFS server returns invalid JSON: %s')
                                  % rawjson)
         return response
 
     def _checkforservererror(self, pointers, responses):
         """Scans errors from objects
 
         Returns LfsRemoteError if any objects has an error"""
         for response in responses:
             error = response.get('error')
             if error:
                 ptrmap = {p.oid(): p for p in pointers}
                 p = ptrmap.get(response['oid'], None)
                 if error['code'] == 404 and p:
                     filename = getattr(p, 'filename', 'unknown')
                     raise LfsRemoteError(
                         _(('LFS server error. Remote object '
                           'for file %s not found: %r')) % (filename, response))
                 raise LfsRemoteError(_('LFS server error: %r') % response)
 
     def _extractobjects(self, response, pointers, action):
         """extract objects from response of the batch API
 
         response: parsed JSON object returned by batch API
         return response['objects'] filtered by action
         raise if any object has an error
         """
         # Scan errors from objects - fail early
         objects = response.get('objects', [])
         self._checkforservererror(pointers, objects)
 
         # Filter objects with given action. Practically, this skips uploading
         # objects which exist in the server.
         filteredobjects = [o for o in objects if action in o.get('actions', [])]
         # But for downloading, we want all objects. Therefore missing objects
         # should be considered an error.
         if action == 'download':
             if len(filteredobjects) < len(objects):
                 missing = [o.get('oid', '?')
                            for o in objects
                            if action not in o.get('actions', [])]
                 raise LfsRemoteError(
                     _('LFS server claims required objects do not exist:\n%s')
                     % '\n'.join(missing))
 
         return filteredobjects
 
     def _basictransfer(self, obj, action, localstore):
         """Download or upload a single object using basic transfer protocol
 
         obj: dict, an object description returned by batch API
         action: string, one of ['upload', 'download']
         localstore: blobstore.local
 
         See https://github.com/git-lfs/git-lfs/blob/master/docs/api/\
         basic-transfers.md
         """
         oid = str(obj['oid'])
 
         href = str(obj['actions'][action].get('href'))
         headers = obj['actions'][action].get('header', {}).items()
 
         request = util.urlreq.request(href)
         if action == 'upload':
             # If uploading blobs, read data from local blobstore.
             with localstore.vfs(oid) as fp:
                 _verifyfile(oid, fp)
             request.data = filewithprogress(localstore.vfs(oid), None)
             request.get_method = lambda: 'PUT'
 
         for k, v in headers:
             request.add_header(k, v)
 
         response = b''
         try:
             req = self.urlopener.open(request)
             while True:
                 data = req.read(1048576)
                 if not data:
                     break
                 response += data
         except util.urlerr.httperror as ex:
             raise LfsRemoteError(_('HTTP error: %s (oid=%s, action=%s)')
                                  % (ex, oid, action))
 
         if action == 'download':
             # If downloading blobs, store downloaded data to local blobstore
             localstore.write(oid, response, verify=True)
 
     def _batch(self, pointers, localstore, action):
         if action not in ['upload', 'download']:
             raise error.ProgrammingError('invalid Git-LFS action: %s' % action)
 
         response = self._batchrequest(pointers, action)
         objects = self._extractobjects(response, pointers, action)
         total = sum(x.get('size', 0) for x in objects)
         sizes = {}
         for obj in objects:
             sizes[obj.get('oid')] = obj.get('size', 0)
         topic = {'upload': _('lfs uploading'),
                  'download': _('lfs downloading')}[action]
         if len(objects) > 1:
             self.ui.note(_('lfs: need to transfer %d objects (%s)\n')
                          % (len(objects), util.bytecount(total)))
         self.ui.progress(topic, 0, total=total)
         def transfer(chunk):
             for obj in chunk:
                 objsize = obj.get('size', 0)
                 if self.ui.verbose:
                     if action == 'download':
                         msg = _('lfs: downloading %s (%s)\n')
                     elif action == 'upload':
                         msg = _('lfs: uploading %s (%s)\n')
                     self.ui.note(msg % (obj.get('oid'),
                                  util.bytecount(objsize)))
                 retry = self.retry
                 while True:
                     try:
                         self._basictransfer(obj, action, localstore)
                         yield 1, obj.get('oid')
                         break
                     except socket.error as ex:
                         if retry > 0:
                             self.ui.note(
                                 _('lfs: failed: %r (remaining retry %d)\n')
                                 % (ex, retry))
                             retry -= 1
                             continue
                         raise
 
         oids = worker.worker(self.ui, 0.1, transfer, (),
                              sorted(objects, key=lambda o: o.get('oid')))
         processed = 0
         for _one, oid in oids:
             processed += sizes[oid]
             self.ui.progress(topic, processed, total=total)
             self.ui.note(_('lfs: processed: %s\n') % oid)
         self.ui.progress(topic, pos=None, total=total)
 
     def __del__(self):
         # copied from mercurial/httppeer.py
         urlopener = getattr(self, 'urlopener', None)
         if urlopener:
             for h in urlopener.handlers:
                 h.close()
                 getattr(h, "close_all", lambda : None)()
 
 class _dummyremote(object):
     """Dummy store storing blobs to temp directory."""
 
     def __init__(self, repo, url):
         fullpath = repo.vfs.join('lfs', url.path)
         self.vfs = lfsvfs(fullpath)
 
     def writebatch(self, pointers, fromstore):
         for p in pointers:
             content = fromstore.read(p.oid(), verify=True)
             with self.vfs(p.oid(), 'wb', atomictemp=True) as fp:
                 fp.write(content)
 
     def readbatch(self, pointers, tostore):
         for p in pointers:
             content = self.vfs.read(p.oid())
             tostore.write(p.oid(), content, verify=True)
 
 class _nullremote(object):
     """Null store storing blobs to /dev/null."""
 
     def __init__(self, repo, url):
         pass
 
     def writebatch(self, pointers, fromstore):
         pass
 
     def readbatch(self, pointers, tostore):
         pass
 
 class _promptremote(object):
     """Prompt user to set lfs.url when accessed."""
 
     def __init__(self, repo, url):
         pass
 
     def writebatch(self, pointers, fromstore, ui=None):
         self._prompt()
 
     def readbatch(self, pointers, tostore, ui=None):
         self._prompt()
 
     def _prompt(self):
         raise error.Abort(_('lfs.url needs to be configured'))
 
 _storemap = {
     'https': _gitlfsremote,
     'http': _gitlfsremote,
     'file': _dummyremote,
     'null': _nullremote,
     None: _promptremote,
 }
 
 def _verify(oid, content):
     realoid = hashlib.sha256(content).hexdigest()
     if realoid != oid:
         raise error.Abort(_('detected corrupt lfs object: %s') % oid,
                           hint=_('run hg verify'))
 
 def _verifyfile(oid, fp):
     sha256 = hashlib.sha256()
     while True:
         data = fp.read(1024 * 1024)
         if not data:
             break
         sha256.update(data)
     realoid = sha256.hexdigest()
     if realoid != oid:
         raise error.Abort(_('detected corrupt lfs object: %s') % oid,
                           hint=_('run hg verify'))
 
 def remote(repo):
     """remotestore factory. return a store in _storemap depending on config"""
     defaulturl = ''
 
     # convert deprecated configs to the new url. TODO: remove this if other
     # places are migrated to the new url config.
     # deprecated config: lfs.remotestore
     deprecatedstore = repo.ui.config('lfs', 'remotestore')
     if deprecatedstore == 'dummy':
         # deprecated config: lfs.remotepath
         defaulturl = 'file://' + repo.ui.config('lfs', 'remotepath')
     elif deprecatedstore == 'git-lfs':
         # deprecated config: lfs.remoteurl
         defaulturl = repo.ui.config('lfs', 'remoteurl')
     elif deprecatedstore == 'null':
         defaulturl = 'null://'
 
     url = util.url(repo.ui.config('lfs', 'url', defaulturl))
     scheme = url.scheme
     if scheme not in _storemap:
         raise error.Abort(_('lfs: unknown url scheme: %s') % scheme)
     return _storemap[scheme](repo, url)
 
 class LfsRemoteError(error.RevlogError):
     pass